how many terms of the AP 43, 39, 35.....must be taken so that their sum is 252
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⭕️Sum of ap = n(2a + (n-1)d) / 2
⭕️For 43, 39, 35, ...
✔️a{First term} = 43
✔️d{Difference i.e a2-a1} = -4
⇒ 252 = n(2 x 43 + (n - 1) x -4) / 2
⇒ 252 = 45n -2n2
⇒ 2n2 - 45n + 252 = 0
⇒ (2n - 21)(n - 12) = 0
⇒ n = 101/2 or 12
✔️101/2th terms don't say accurately which term... so this cannot be an answer......
✔️Thus 12 terms are needed.
⭕️For 43, 39, 35, ...
✔️a{First term} = 43
✔️d{Difference i.e a2-a1} = -4
⇒ 252 = n(2 x 43 + (n - 1) x -4) / 2
⇒ 252 = 45n -2n2
⇒ 2n2 - 45n + 252 = 0
⇒ (2n - 21)(n - 12) = 0
⇒ n = 101/2 or 12
✔️101/2th terms don't say accurately which term... so this cannot be an answer......
✔️Thus 12 terms are needed.
rahimkhan2:
hello
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the required terms is 12
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